Hi Jason,
Firstly, there won't be a big difference between one CBE to another if they are both straight through designs on a naturally aspirated engine.
Secondly, the smaller diameter pipes of the baseline invidia runs will indeed make more torque in the mid 2K RPM range. I've dyno tested the same thing with both 2.25" and 2.5" primary tubes on the XYZ pipe during development testing. I found this same difference of low end torque on the smaller pipes too but I also found the smaller primary pipes lose 2-3HP over a fairly wide range of high RPM. So the trade was made for more top end by selecting 2.5" primaries on the XYZ pipe.
Thirdly, a different state of tune. The baseline condition was fully tuned for both timing and A/F ratio. The post Shockwave))) dynos were retuned but only for A/F ratio. Although the final pre/post power numbers were the same in this test, differences of power curve smoothness (or lack thereof) shows that the two are not tuned to the same power threshold.
When a tune pushes the engines power curve to its absolute limit, the power curve starts to show a lumpy or wavy character as the engine pushes into the threshold of ping. (this lumpyness is seen in the baseline plots). The baseline tune was completely maxed out. The baseline power curve "lumpyness" is indicating that no more power can be made.
However, for the post testing, it was retuned but only for A/F ratio. There was no re-optimization of spark timing. Although spark timing was not retuned for the Shockwave))) it can be seen in the dyno plots that its power curve was smoother and much more consistent from run to run. Curve smoothness shows the post dyno runs are clearly below the threshold of ping. Smoothness of the Shockwave))) power curves indicates its was not maxed out. In my analysis, if the post Shockwave))) runs were also tuned for spark timing it would have made more gains.
As for loudness, the Shockwave))) is designed to be a loud exhaust but it will quiet down a bit once the mufflers break in at 2K-3K miles.
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